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PHEVs release nearly 5x more global warming pollution than lab-reported data show, according to a new analysis.

Growing Discrepancy In Official and Real-World CO2 Output

Data shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit group. That differs significantly with laboratory tests, which assumed a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” stated a senior analyst participating in the report. “This discrepancy is widening and creates a serious issue. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode relative to total mileage. The team found that only 27% of driving was done in EV mode, whereas lab estimates assumed 84%.

Even, when operating in electric mode, pollution amounts were well above official estimates. This occurred because EV motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed several large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 more annually in running costs than is assumed under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Lobbying

Hybrid cars have recently been brought back into policy discussions as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large automotive industries.

Several high-level politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An external energy economics specialist, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the car sector claimed there was too little information to properly evaluate actual emissions.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be made with utmost care and considering that data.”